Brake head-centering device for railway brake apparatus

ABSTRACT

The disclosure concerns brake apparatus for railway cars and locomotives in which the brake head is journaled on a pivoting hanger and is centered by a biasing spring. The hanger is moved by an elongated actuating member having a substantially fixed orientation with respect to the horizontal, and a four-bar parallelogram linkage orients the seat of the biasing spring relative to the actuating member so as to maintain alignment of the head with respect to the braking surface of the wheel during pivotal movement of the hanger.

7 United States Patent Engle 1451 Oct. 10, 1972 541 BRAKE HEAD-CENTERINGDEVICE 2,480,073 8/1949 Barrows ..188/212 x FOR RAILWAY BRAKE APPARATUS2,588,645 3/1952 Miers 1 88/212 Inventor:

[72] Thomas H. Engle, Cape Vincent,

Assignee: General Signal Corporation Filed: Feb. 8, 1971 Appl. No.2113,280

US. Cl ..l88/2l2, 188/52 Int. Cl ..F 16d 65/06 Field of Search ..l88/52,209, 212, 213, 231

[56] References Cited UNITED STATES PATENTS 12/1918 Cremean ..l88/2l2 X'2/1939 Baselt ..l88/2l2 X Primary Examiner-Duane A. Reger AttorneyDodge& Ostmann ABSTRACT 4 Claim, 4 Drawing Figures minim SHEET 2 4 FIG-2THOMAS ENGLE ATTORNEYS PATENTEDBBT 10 m2 3.696 892 SHEET 3 BF 4 INVENTORTHOMAS H. ENGLE BY i ATTORNEYS PATENTEnuctiomn 3.696.892

SHEET 8 0F 4 FIG-4 INVENTOR THOMAS H. ENGLE BY Q EWV ATTORNEYS BRAKEIIEAD-CENTERING DEVICE FOR RAILWAY BRAKE APPARATUS BACKGROUND ANDSUMMARY OF THE INVENTION In the most common type of railway brake, thebrake shoe for each wheel is attached to a head journaled on a pivotcarried by a hanger which itself depends from a pivot supported by thetruck frame. The head is equipped with a centering device which isintended to keep it aligned with the braking surface of the wheel whenthe brakes are released and thereby prevent dragging of the shoe.Several kinds of centering devices have been proposed. One type consistsof a leaf spring which reacts between the head and a cam surface on thehanger, and which biases the head toward a prescribed position relativeto the hanger in which the shoe is supposed to be aligned with themating rotary braking surface. The simplicity of this approach makes itappealing; however, it is not satisfactory in cases where thebrake-actuator includes a slack adjuster and a small running clearancebetween the shoe and the wheel is to be maintained. The reason for thisis that the slack adjuster progressively changes the release position ofthe hanger as the shoes wear during service. Since the centering deviceorients the head with respect to the hanger, it follows that theorientation of the head relative to the wheel will change. With smallshoe clearances, this change can cause the shoe to rub on the wheelunder release conditions.

A better approach to the head-centering problem is to use a frictionclutch or yielding latch which retards tilting movement of the headrelatively to the hanger, but allows the head to pivot as required toalign the shoe with the wheel under the action of the braking forcedeveloped during a brake application. While,

. from the theoretical standpoint, this solution is capable ofmaintaining a satisfactory degree of shoe alignment, experienceindicates that, as the parts wear during service, the clutch or latchtends toslip and become unreliable.

ln installations employing a direct acting actuator, i.e., an actuator,such as the one disclosed in U.S. Pat. No. 3,512,615, granted May 19,1970, which is attached to the hanger at the head pivot, the centeringproblem can be solved easily by using the' leaf spring mentioned earlierand allowing it to seat on a cam surface carried by the actuator. Sincethe orientation of the actuator with respect to the horizontal changesvary little under service conditions, the leaf spring always biases thehead to the same orientation with respect to the wheel regardless of theangular position of the hanger. Thus, proper shoe-wheel alignment isachieved in a relatively simple and reliable manner. Unfortunately, thissolution is not available in the more common case where spaceconsiderations require that the actuator be located below the horizontalplane containing the head pivot, and the hanger, in effect, becomes aforce-multiplying link.

The object of this invention is to provide a simple and reliable brakehead-centering device which performs the centering function as well asthe device last mentioned and can be applied to installations whereinthe actuator is attached to the hanger at a point offset from the headpivot. According to the invention, the brake head is equipped with abiasing spring which orients it with respect to a seat journaled on apivot carried. by the hanger, and the brake apparatus incorporates afour-bar parallelogram linkage which maintains a prescribed orientationof that seat relative to the hanger actuator. The orientation of theactuator with respect to the horizontal varies only slightly duringpivotal movement of the hanger, and therefore proper correlation of theorientation of the seat relative to the actuator produces the desiredresult of maintaining alignment of the brake shoe with respect to thewheel. And, since the parallelogram linkage is inherently simple and, incontrast to the friction clutches and latches of the prior art, affordspositive control over relative motion between the head and the hanger,centering action is afforded in an economical and reliable manner.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiment of theinvention is described herein with reference to the accompanyingdrawings in which:

FIG. 1 is a side elevation view of a tread brake installation for afour-wheel truck.

FIG. 2 is an enlarged view of the brake unit for one of the wheels shownin FIG. 1.

FIG. 3 is a sectional view, on slightly reduced scale, taken on line 3-3of FIG. 2.

FIG. 4 is a sectional view, on slightly enlarged scale, taken on line 44of FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENT The brake apparatus shown in FIG. 1includes two of the improved braking units 11 equipped with flangedshoes 12 arranged to coact with the treads of the wheels 13 and 14,respectively, on one side of a fourwheel truck. The units are supportedby the truck frame 15 and are actuated by a common hydraulic brakecylinder 16 which is hung between them in a position inboard of theequalizer bar 17. Cylinder 16 comprises relatively movable cylinder androd elements 18 and 19, respectively, which are pivotally connected tothe lower ends of hangers 21, and also includes a lock mechanism 22which enables the apparatus to serve as a hand brake. Preferably,mechanism 22 is constructed in accordance with the teachings inapplication Ser. No. 882,655, filed Dec. 5, 1969. The wheels at theopposite side of the car are provided with an identical brake apparatus,and the hydraulic lines 23 for the two cylinders and lock mechanisms arejoined to the cars hydraulic circuit by a tee and bleed fitting 24attached to the car body. It is preferred that this circuit beconstructed in accordance with the teachings in U.S. Pat. Nos.3,508,794, granted Apr. 28, 1970, and 3,513,656, granted May 26, 1970.

As shown in FIGS. 2-4, the hanger 21 of each brake unit 11 is aone-piece casting including spaced side members 21a and 21b and anintermediate, joining web 210. The hanger depends from a pivot bolt 25which is journaled in a bracket 26 attached to a pad 27 cast integrallywith the truck frame 15. At their lower ends, the side members of hanger21 are bridged by a second pivot bolt 28 on which is journaled thefitting 29 carried by the rod element 19 of brake cylinder 16, andwhich, therefore serves as the pivotal connection for the brakecylinder. Intermediate the two pivots 25 and 28, members 21a and 21b arebridged by a third bolt 31 which serves as the pivot for a brake head 32to which shoe 12 is attached.'Bolt 31 also serves as a pivot for a cammember 33 which is positioned between the integral ears or legs 32a and32b of head 32. The cam is formed with a flat seating surface 34 whichis engaged by the intermediate portion of a leaf spring 35 whoseopposite ends are held captive by a pair of transverse pins 36 extendingthrough head 32. The spring 35 tends to assume the illustrated nullposition in which it lies flat against surface 34, and consequently itbiases the head about pivot31 to a prescribed angular position withrespect to cam member 33. The spring is stiff enough to hold the head inthis position under service conditions whenever the brakes are released,but not so stiff as to preclude the head motion required during a brakeapplication to accommodate conditions such'as out-of-round wheels andvertical movement of pivot 25 relatively to the axle.

As shown most clearly in FIG. 4, cam member 33 is joined to rod fitting29 by an articulated link 37 whose opposite ends are journaled on pins38 and 39 carried by these members. It also will be observed in thisFigure, that the axes of pivots 28, 31, 38 and 39 are located at thecorners of a four-bar parallelogram A-B- C-D made up of portions ofhanger 21, fitting 29, cam member 33 and link 37. This four-bar linkageinherently maintains parallelism between bars B and D during pivotalmovement of hanger 21, and therefore fixes the orientation of camsurface 34 relative to the axis of cylinder 16. Since the cylinder is along member and its axis remains substantially horizontal throughoutservice, and spring 35 fixes the orientation of head 32 relative tosurface 34 when the brakes are released, it follows that the angularposition of the head in space under release conditions will remainfixed. Thus, if the inclination of surface 34 with respect to thevertical is selected initially to provide concentricity between shoe 12and the tread of wheel 13, this alignment will be maintained duringservice regardless of the fact that the angular position of hanger 21under release conditions changes as slack is taken up. Of course, sincepivot 25 does move vertically with respect to the axle, and pivot 31moves in an are about pivot 25, and not on a true radius of wheel 13, asthe hanger pivots, it is evident that perfect alignment cannot bemaintained. However, as those skilled in the art will realize, thedegree of alignment which is afforded is satisfactory.

Although the brake head-centering scheme of this invention can beemployed in various types of brake rigging, the one which has beenillustrated is particularly desirable because it facilitatesmaintenance. Servicing of the components requires only removal of thepivot bolts 28'at the ends of cylinder 16, and, unless shop repair orreplacement of the cylinder itself is needed, the hydraulic lines 23need not be opened.

While the invention has been described in connection with tread brakesfor a four-wheel truck, it should be obvious that it is equally usefulin other applications. For example, in the case of tread brakes for asix-wheel truck, the center and one outside wheel on each side arehandled as shown in FIG. 1, and the remaining wheel on each side isequipped with another brake unit 1 1 which is provided witha separatehydraulic cylinder pivotally connected to the truck frame. In the caseof disc brake uni on t e other hand, the c l' der 16 is arrangedparallel wit the axle, and the 11 are hung adjacent the brake platesattached to the hubs of the two wheels on the axle. Here, of course, thebrake shoe 12 takes the form of the separate brake blocks normally usedin disc brakes, and head 21 is designed to accept this type of brakingelement.

I claim:

1. Brake apparatus for a wheel of a vehicle comprisa. a hanger (21)depending from a pivot (25) sup ported by a portion (15) of the vehicle;

b. a brake head (32) carrying a shoe (12) arranged to coact with abraking surface of the wheel and journaled on a pivot (31) supported bythe hanger;

c. spring means (35) reacting between the head (32) and a movable seat(33) carried by the hanger and biasing the head toward a prescribedorientation relative to the seat; and a four-bar parallelogram linkage(A, B, C,'D) connected to the. seat (33) and serving, during pivotalmovement of the hanger (21 to change the orientation of the seatrelative to the hanger as needed to maintain alignment of the shoe withrespect to said braking surface. Brake apparatus as defined in claim 1which a. includes an elongated actuating member (16) having asubstantially fixed orientation relative to the horizontal and connectedwith the hanger (21) for moving the latter about its pivot (25); and b.the parallelogram linkage (A, B, C, D) is connected to maintain aprescribed orientation of the seat (33) relative to the actuatingmember. Brake apparatus as defined in claim 2, in which a. the actuatingmember (16) is connected to the hanger (21) by a pivot (28) located at agreater moment arm with respect to the hanger pivot (25) than the headpivot (31); the seat (33) is journaled on the head pivot (31);

and c. the four bar parallelogramlinkage (A, B, C, D) includes portionsof the seat (33), the hanger (21) and the actuating member (16, 29), alink (37) pivotally connected to the seat (33) and the actuating member(16, 29), and the head pivot (31), the actuating member pivot (28) andthe pivots (38, 39) ofsaid link (37). Brake apparatus as defined inclaim 2, including a. an additional hanger (21), brake head (32), springmeans (35), seat (33) and four-bar parallelogram linkage (A, B, C, D) asdescribed previously and associated with a second wheel (14) of thevehicle; and b. in which said actuating member is a horizontal brakecylinder (16) located between the two wheels (13, 14) and pivotallyconnected at its opposite ends to the two hangers (21).

1. Brake apparatus for a wheel of a vehicle comprising a. a hanger (21)depending from a pivot (25) supported by a portion (15) of the vehicle;b. a brake head (32) carrying a shoe (12) arranged to coact with abraking surface of the wheel and journaled on a pivot (31) supported bythe hanger; c. spring means (35) reacting between the head (32) and amovable seat (33) carried by the hanger and biasing the head toward aprescribed orientation relative to the seat; and d. a four-barparallelogram linkage (A, B, C, D) connected to thE seat (33) andserving, during pivotal movement of the hanger (21), to change theorientation of the seat relative to the hanger as needed to maintainalignment of the shoe with respect to said braking surface.
 2. Brakeapparatus as defined in claim 1 which a. includes an elongated actuatingmember (16) having a substantially fixed orientation relative to thehorizontal and connected with the hanger (21) for moving the latterabout its pivot (25); and b. the parallelogram linkage (A, B, C, D) isconnected to maintain a prescribed orientation of the seat (33) relativeto the actuating member.
 3. Brake apparatus as defined in claim 2, inwhich a. the actuating member (16) is connected to the hanger (21) by apivot (28) located at a greater moment arm with respect to the hangerpivot (25) than the head pivot (31); b. the seat (33) is journaled onthe head pivot (31); and c. the four-bar parallelogram linkage (A, B, C,D) includes portions of the seat (33), the hanger (21) and the actuatingmember (16, 29), a link (37) pivotally connected to the seat (33) andthe actuating member (16, 29), and the head pivot (31), the actuatingmember pivot (28) and the pivots (38, 39) of said link (37).
 4. Brakeapparatus as defined in claim 2, including a. an additional hanger (21),brake head (32), spring means (35), seat (33) and four-bar parallelogramlinkage (A, B, C, D) as described previously and associated with asecond wheel (14) of the vehicle; and b. in which said actuating memberis a horizontal brake cylinder (16) located between the two wheels (13,14) and pivotally connected at its opposite ends to the two hangers(21).